trigger DeletePO on Account (after delete) {
   
 for (Account a :Trigger.old){     
    decimal Accid;      
    Accid = a.Oracle_Account_Number__c;     
                 
    Purchase_Object__c []  pos = [SELECT ID from Purchase_Object__c ps where (ps.Oracle_Acc_Number__c = :Accid)];        
                   
     try {
    delete pos;
        } catch (DmlException e) {
    // Process exception here 
    
        }                     
                  
    }   
   }